In an existing E-UTRA (evolved UMTS terrestrial radio access) system, an OFDM (orthogonal frequency division multiplexing) technology is used in a downlink, and an SC-OFDM (single-carrier orthogonal frequency division multiplexing) technology is used in an uplink. In uplink transmission, a user may transmit uplink control information (UCI). The UCI may include ACK/NACK feedback information in a hybrid repeat mechanism, rank indication (RI) information related to a channel state, channel quality information (CQI), and precoding matrix information (PMI).
The UCI may be transmitted periodically, and may also be transmitted aperiodically, such as transmission based on triggering. The UCI may be transmitted via a physical uplink control channel (PUCCH), and may also be transmitted via a physical uplink shared channel (PUSCH). When the UCI is transmitted via the PUSCH, it may be multiplexed with uplink data, and also be transmitted separately without uplink data.
In an existing system, when the UCI is transmitted in the PUSCH, each time slot of each subframe has OFDM symbol(s) for transmitting the UCI, and the UCI is mapped onto time-frequency resources in a mapping manner of time domain first. For example, ACK/NACK control information is mapped into four OFDM symbols neighboring uplink reference signals (RSs), and RI information is mapped into four OFDM symbols neighboring the OFDM symbols occupied by the ACK/NACK, with both types of the UCI being mapped from bottoms of frequency band resources occupied by a PUSCH to tops. CQI/PMI occupies all OFDM symbols in the time domain, and is mapped from the tops of the frequency band resources occupied by the PUSCH to the bottoms, which are followed by uplink data. Rate matching is performed on the uplink data according the RI information and the CQI/PMI, while the ACK/NACK is mapped into the PUSCH by puncturing uplink data at corresponding positions.
As great increase of smart terminals, in further evolvement of a future LTE-advanced system, it is possible that a legacy macro base station (Macro cell) is unable to deal with such rapidly increased demands for capacities and peak value rates. Users may be made to be more close to a base station by deploying base stations more densely, thereby improving system capacities, increasing peak value rates and improving user terminal experiences. However, deployment of high-power macro base stations will result in problems of over high cost, and non-green communication, etc. Hence, people are starting to consider a small base station (small cell) of low power (such as a pico cell, a Femto cell, and a remote radio head (RRH)). In comparison with a macro base station, a small base station is advantageous in low cost, fast and flexible deployment and high cost performance. Thus, small base stations are applicable to outdoor hot spots, increase network capacities, improve indoor deep coverage, and increase user perception.
Therefore, small base stations are drawing more and more attention of the industry. In a future LTE-Advanced network, the number of small base stations will exceed that of legacy macro base stations. Coverage of a small base station is smaller than that of a macro base station, and may use a higher available frequency band, such as 3.5 GHz; while a macro base station follows to use an existing relatively low frequency band, so as to provide relatively large and robust coverage.
However, it was found by the inventors that typical serving objects of a small base station are low-speed moving or stationary users with relatively small multi-path delay expansion. Hence, when a user is served by a small base station, a change of its channel is slow, which may be deemed as being relatively flat in the time dimension or the frequency domain dimension. And in an existing system, an uplink reference signal still occupies two OFDM/SC-FDMA symbols in a subframe, which results in waste of resources, and is disadvantageous to further improving performance of the system.
It should be noted that the above description of the background is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.